1. Field of the Invention
The invention relates generally to self-organized polymolecular structures and in particular, to helical, tubular and needle-like structures formed by the association of amphiphilic tartaric acid derivatives and bipyridine compounds.
2. Description of the Related Art
Materials of defined morphologies, such as polymolecular tubular or helical structures, have many practical uses, including as vehicles for controlled-release drug delivery, as reinforcing material for high strength composites and as components of radar absorbing materials.
Currently known materials of defined morphologies include structures formed by molecular self-assembly of single molecular components such as amphiphiles (for example, phospholipids). Amphiphiles are compounds that have a hydrophobic portion and a hydrophilic portion. In an aqueous solution, the hydrophobic portions of adjacent molecules tend to congregate, thereby creating a polymolecular structure. For example, U.S. Pat. No. 5,290,960 to Singh describes tubular microstructures formed by the self-assembly of diacetylenic phospholipids. The technical utility of diacetylenic phospholipid-derived tubules for applications such as controlled release drug delivery has been demonstrated, but the practical usefulness of these materials is limited because of their high cost and poor shelf life.
Self organized structures have also been formed by the non-covalent interactions (such as hydrogen bonding) between complementary molecular building blocks. Such structures are described, for example, in the following publications, incorporated herein by reference: J. -M. Lehn, "Supramolecular Chemistry: Concepts and Perspectives" published by Verlag Chemie, Weinheim, pp 139-197, (1995); C. P. Lillya et al., "Linear Chain Extension Through Associative Terminii", Macromolecules, 25, 2076-2080, (1993); R. P. Sijbesma et al., "Reversible Polymers by Quadruple Hydrogen Bonding", Science, 278, 1601-1604, (1997); T. Kato, "A Liquid Crystalline Polymer Network Built by Molecular Self-Assembly Through Intermolecular Hydrogen Bonding", Angew. Chem. Int. Ed. Engl., 33, 1644, (1994); C. M. Paleos and D. Tsiourvas, Angew. Chem. Int. Ed. Engl., 34, 1696-1711, (1995) and G. Whitesides et al., Non-covalent Synthesis, Acc. Chem. Res., 28, 1, 1995. Intermolecular hydrogen bonding between compounds containing pyridine groups and compounds containing carboxyl groups is described in the following patents and publications, incorporated herein by reference: U.S. Pat. No. 5,037,574 to Frechet et al; U.S. Pat. No. 5,139,696 to Frechet et al; Kihara et al, "Supramolecular Liquid-Crystalline Networks Built by Self-Assembly of Multifunctional Hydrogen-Bonding Molecules", Chem. Mater., Vol 8, No. 4 (1996), pp 961-968; Kato et al, "Cooperation of Hydrogen Bonds for Mesophase Stabilization in Supramolecular Assemblies", Chemistry Letters 1997, pp 1143-1144; Kihara et al, "Induction of a Cholesteric Phase via Self-Assembly in Supramolecular Networks Built of Non-Mesomorphic Molecular Components" Liquid Crystals, 1998, Vol. 24, No. 3, pp. 413-418; and Mallia et al "Photochemical Phase Transition in hydrogen-Bonded Liquid Crystals," Chem. Mater 1999, 11, pp 207-208.